The present invention relates to an active matrix type liquid crystal display apparatus.
The active matrix type liquid crystal display apparatus using active elements represented by a thin film transistor (TFT) is becoming popular as display terminals of office automation (OA) apparatus and other equipment in view of the fact that it is thin, light weight, and has a high image quality comparable to a Braun tube. The display type of liquid crystal display apparatus can be divided roughly into two categories. The one is a type wherein the liquid crystal is held between two substrates whereon transparent electrodes are formed, the liquid crystal is operated by voltage applied to the transparent electrodes, and an image is displayed by modulating incident light into the liquid crystal through the transparent electrodes. All of the various makes of liquid crystal display apparatus used widely at the present time adopt the above described display type. The other one is a type wherein the liquid crystal is operated by an electric field which is disposed in parallel to a substrate plane between two electrodes composed on the similar substrate, and an image is displayed by modulating incident light into the liquid crystal through a gap between the two electrodes. That display type has not been adopted in any apparatus yet, but it has preferable features, such as wide viewing-angles, a low load capacitance, and other desirable characteristics; and accordingly, the technology of the latter display type is promising in the field of active matrix type liquid crystal display apparatuses. The above feature are disclosed in JP-T-5-505247 (1993), and JP-B-63-21907 (1988).
However, the display type wherein the liquid crystal is operated by an electric field which is approximately in parallel with the substrate has problems, such as a small aperture area for transmitting light, a dark image display, and a requirement for bright back light with high power consumption in order to solve the dark image display problem, because opaque electrodes are composed in a comb-teeth shape. Therefore, it is necessary to decrease the number of electrodes and wiring to connect the electrodes as much as possible in order to extend the aperture area, that is, to improve the aperture ratio. When an electrode having a different potential from that of the two electrodes approaches the two electrodes controlling the orientation of the liquid crystal, the orientation of the liquid crystal is disturbed, and an orientation failure domain is generated. As the result, the effective aperture area decreases, and a problem, such as a decrease in the aperture ratio, is generated. Therefore, it is necessary to decrease the orientation failure domain, and to increase the effective aperture ratio.